1. Field of the Invention
The present invention relates to a deflection yoke for a cathode ray tube, and more particularly, to a saddle-saddle type deflection yoke for a cathode ray tube, which has a magnet for canceling a leakage magnetic field coming from the deflection yoke.
2. Background of the Related Art
A related art deflection yoke has a horizontal deflection coil having a current of very low frequency of 15.75 KHz or over applied there to synchronous to a video signal and a vertical deflection coil 30 having a current of extreme low frequency applied thereto. The vertical and horizontal deflection coils having the current applied there to generate vertical and horizontal magnetic fields respectively, to deflect electron beams emitted from the electron gun to a given region on a screen. In the meantime, because the magnetic field from the current of the very low frequency might harm the human body, there have been many suggestions which can prevent leakage of magnetic field from the cathode ray tube caused by the very low frequency current.
FIG. 1 illustrates a perspective view of a related art deflection yoke for a cathode ray tube disclosed in Korea Patent publication No. 96-7241, and FIG. 2 illustrates a longitudinal section of the deflection yoke in FIG. 1, schematically.
Referring to FIGS. 1 and 2, the related art deflection yoke 10 is provided with horizontal and vertical deflection coils 20 and 30 for deflecting electron beams emitted from an electron gun, a ferrite core 40 disposed to surround an outer side of the vertical deflection yoke for improving a magnetic efficiency, a holder 50 for fixing positions of the horizontal and vertical deflection coils 20 and 30 and the ferrite core 40 and insulating between the horizontal and vertical deflection coils 20 and 30, and cancel coils 531 and 532 wound on bobbins 52 respectively fitted to an upper side and lower side of a flange formed on a screen side of the holder 50.
FIG. 3 illustrates a circuit showing connection of the horizontal deflection coil 20 and the cancel coils 531 and 532.
Referring to FIG. 3, each of the cancel coils 531 and 532 is connected to a circuit of the horizontal deflection coil 20, and is connected in series. The cancel coils 531 and 532 are connected to the horizontal deflection coil 20 for generating magnetic fields from a screen side of the holder 51 opposite to the leakage magnetic field generated in the horizontal deflection coil 20. According to this, as shown in FIG. 2, the cancel coils 531 and 532 can cancel the leakage magnetic field from the horizontal deflection coil 20 at the screen side of the deflection yoke 10 for preventing leakage of the magnetic field of the horizontal deflection coil.
However, the related art cancel coils 531 and 532 has the following problems.
First, as inductances of the cancel coils 531 and 532 are added to an inductance of the horizontal deflection coil 20, the inductance of the horizontal deflection coil 20 should be reduced, which drops a horizontal deflection power of the horizontal deflection coil, to reduce a size of an image. However, if a horizontal deflection current is increased for enlarging the image size, a heat generation characteristic of the deflection yoke 10 is deteriorated, to drop a performance of the deflection yoke 10.
Second, during the horizontal deflection current is fed back, a current charged in the cancel coils 531 and 532 wound on the bobbins 52 is discharged. FIG. 4 illustrates an example of ringing of an image caused by discharge of a current from the cancel coils 531 and 532. Though the ringing may be prevented by providing a resistor 60 and a condenser 70 parallel to the cancel coils 531 and 532, it results increased numbers of components and production man-hours.
Accordingly, the present invention is directed to a deflection yoke for a cathode ray tube that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a deflection yoke for a cathode ray tube, which causes no performance drop and can cancel a leakage magnetic field coming from a deflection yoke without addition of any components.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the deflection yoke for a cathode ray tube includes horizontal and vertical deflection coils for deflection of electron beams emitted from an electron gun in horizontal and vertical directions, respectively, a ferrite core disposed to surround the vertical deflection coil for improving a magnetic efficiency, a holder adapted to fix positions of the horizontal and vertical deflection coils and the ferrite core and insulate the horizontal and vertical deflection coils, and a magnetic material provided on an upper side and a lower side of a flange part formed at a screen side of the holder for canceling a magnetic field leaked from the horizontal deflection coil at the screen side of the holder.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.